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Big boom You know when you're having a bad day when you get hit by a billion-tonne asteroid. But for a pulsar 37,000 light-years away, it's just another day at the office.

Astronomers made the discovery while using the Parkes Telescope in Australia and the Hartebeesthoek Radio Astronomy Observatory in South Africa to study the dusty, high-radiation environment surrounding the tiny spinning husk of the pulsar PSR J0738-4042.

Pulsars are spinning compact stellar objects known as neutron stars that generate powerful beams of radiation from their intensely magnetised poles that. If aligned correctly with Earth, these beams can be observed as ultra-precise radio pulses.

These objects are considered the most precise 'clocks' in the universe, but if a pulsar's pulse timings abruptly change, it is likely that a cataclysmic event likely occurred.

In the case of PSR J0738-4042, the astronomers noticed weird changes in the pulsar's timing and its characteristic pulse, signals that the researchers have attributed to multiple asteroid hits.

In 2008, Shannon theorised that should a large rocky object, like an asteroid or even a small planet, collide with a pulsar, the pulsar will react in a very precise way. Now it seems PSR J0738-4042 has become the prime candidate as observational evidence for this theory. The time of the pulse has lengthened and the radio signal received by Parkes has changed.

"We think the pulsar's radio beam zaps the asteroid, vaporising it. But the vaporised particles are electrically charged and they slightly alter the process that creates the pulsar's beam," says Shannon.

The electrically charged particles interact with the pulsar's magnetic field, sapping some of the pulsar's angular momentum. This has a drag effect, slowing the spin rate. However, once all the ionised material has been converted to energy, the pulsar is expected to return to its pre-asteroid strike spin rate.

Surviving the supernova

It is thought that the surrounding asteroids originated from the star that exploded to form the pulsar.

This asteroid-vaporising event is exciting in that it proves that rocky debris that formed before the star went supernova persisted after the star's death, forming a debris disk around PSR J0738-4042.

It's possible that the surviving debris disk could be rejuvenated, spawning the agglomeration of larger and larger objects, potentially forming new planets.

The discovery of asteroid vaporisation events close to PSR J0738-4042 is an interesting development in the study of disks surrounding pulsars.

"This sort of dust disk could provide the 'seeds' that grow into larger asteroids," says study co-author Paul Brook, a PhD student of the University of Oxford and CSIRO.

Another pulsar, J0146+61, has been found to be sporting a dusty debris disk and, in 1992, two planet-sized objects were discovered orbiting pulsar PSR 1257+12.

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